Valveless pulse jet engine having electric arc heating means



Feb- 12, 1952 G. E. MALLlNcKRoDT 2,585,810

VALVELESS PULSE JET ENGINE HAVING ELECTRIC ARC HEATING MEANS Filed oct.26, 1945 2 SHEETS-SHEET 1 .TNR www Feb. 12, 1952 G. E. MALLINCKRODTVALVELESS PULSE JET ENGINE HAVING ELECTRIC ARC HEATING MEANS 2 SHEETS-SHEET 2 Filed Oct. 26, 1945 Patented Feb. 12, 1952 UNITED STATES2,585,810 PATENT OFFICE VALVELES S PULSE `YET ENGINE HAVING 6 Claims.

This invention relates to jet propulsion apparatus, and with regard tocertain more specic features, to electric arc apparatus of this classfor propelling airplanes and the like.

Among the several objects of the invention may be noted the provision ofa simple jet propulsion unit having no relatively moving mechanicalparts; the provision of apparatus of the class described which operatesat feasible temperatures, thus decreasing structural problems; theprovision of a unit of the class described having substantial thrustcapacity and thermodynamic emciency; and the provision of a device ofthis class in which the eiiciency is substantially maintained at highspeeds. Other objects will be in part obvious and in part pointed outhereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and arrangements of parts which willbe exemplified in the structures hereinafter described, and the scope ofthe application of which will be indicated in the following claims.

In the accompanying drawings, in which one of various possibleembodiments of the invention is illustrated,

Fig. l is a top plan view of one jet propulsion unit;

Fig. 2 is a side elevation of Fig. 1;

Fig. 3 is an enlarged'fragmentary vertical section taken on line 3 3 ofFig. 1;

Fig. 4 is an enlarged left-end View taken on line 4 4 of Fig. 2;

Fig. 5 is an enlarged vertical section taken on line 5 5 of Figs. 1 and3;

Fig. 6 is an enlarged vertical section taken on line 6 5 of Figs. l and3;

Fig. 7 is an enlarged rear end elevation viewed from line 'I 'l of Fig.2;

Fig. 3 is a circuit diagram; and

Fig. 9 is a plan view of an airplane showing how the invention isincorporated.

Similar reference characters indicate corresponding parts throughout theSeveral views of the drawings.

Hereinafter one jet propulsion unit is described, but it is to beunderstood that these units may be used either singly or in multiple onairplanes and the like. For example, they may be mounted on center linesas indicated in Fig. 9. It is to be understood that the dimensionsspecified herein are exemplary and that variations may be made to suitparticular designs.

Referring now more particularly to Figs. l and 2, each propulsion unitis indicated by numeral I. Broadly, it consists of an elongateheatresistant metal tube of increasing rectangular cross section,progressing from the front (shown at the left) to the rear (shown at theright). The width of the tube as indicated in Fig. 1 is preferablyconstant, for example of the order of 4 inches. The depth as shown inFig. 2 varies. For example, at the inlet opening 3 it is 3 in. deep. Atpoint 5 (section 5 5) which is 4 ft. removed from the front 3, it is31/2 in. deep. At point 'I (section 6 5) which is 12 ft. behind point 5,it is 6 in. deep, and at the rear end 9, 4 ft. removed from point "I, itis 12 in. deep. All of the stated dimensions may be considered to beinside dimensions. The wall thickness is chosen to be suicient forstructural purposes.

The respective tapers between points 3, 5, 'l and 9 are preferablycontinuous. The section of the tube between points 3 and 5 will bereferred to as an inlet nozzle or chamber I. The section between points5 and 'I will be referred to as the energy transformation or arc chamberT. The section between points I and 9 will be referred to as the exhaustsection E. Each unit I is installed in an airplane or the like with itsaxis parallel to the direction of motion of the airplane (see the centerlines of Fig. 9). Thus the units may be located chordwise in the wings,along the fuselage, or the like. Forward motion of the airplane willcause air to be enveloped in the moving inlet section I. This inletsection I is simply an air-receiving tube which, by reason of itsrearward expansive taper, reduces the friction of rearward ow to thepoint 5.

The upper and lower portions of the transformation section T are linedby channel-shaped, heat-resistant, insulating members I i, composed, forexample, of spark-plug porcelain, mica or the like. These members havetubular lugs I3 and I5 at intervals, which extend through opening I1 inthe tube T. Cupped bushings I9, composed of similar material, engage thelugs I3-I5 on the outside. Fastening bolts 2I extending through the lugsI3 and bushings I9 serve to hold the liners II in place. Some of thesebolts ZI also function as electrical terminals, as will appear.

The inside heads 23 of the bolts 2| hold conductivetemperature-resistant strips 25, the edges of which are offset, asindicated, to receive flanged base portions 2l of elongate carbon strips29 forming electrodes. The strips 25, as well as the bolts 2i, are alsocomposed of high-temperature alloy or beryllium. Other than carbon maybe used for the electrodes 26, provided said other material has therequisite properties of electrodes in the described locations.

Each electrode 2t is thus insulated from the tube T and extendsapproximately from the point 5 to the point 'l 12 ft.). Near their frontends and just behind the point 5, the electrodes are provided withprotrusions 3i, leaving an approximately 1/4 in. arc gap 33. An arc isstruck at this gap 33 and proceeds rearwardly along the electrodes, thearc length increasing as it moves rearward to the point l. Movement tothe rear is caused by a sweep of air through the tube T from the inlettube I. At about point I the extended arc becomes extinguished.

aceaeio The arc is established by means of a circuit 3l such as shown inFig. 8, wherein the terminals 35 are connections to opposite ones ofsaid electrodes 2S. Two or more of the bolts 2| may be used for thepurpose. In the circuit 31 is a starting switch i3 and an inductance 3S.An enginedriven A. C. generator' is shown at 4i. The generator 4| is oneexample oi any suitable generator for the electrical energy required. Inthe present case the generator Ill is driven from a suitable engine, somarked. Circuit values are, for example, as iollows:

For the generator iii, 400 cycles per second at 15,000 volts;

For the inductance coil enough reactive impedance so that it, with thereactive impedance in the remainder of the circuit and generator, willtotal il, ohms;

For the generator lll, 50 kw. at 6.5 amp.

The resistance in the arc when it becomes 3 in. long is approximately2,3 d ohms.

Operation is as follows:

It is to be assumed that the vehicle in which the jet propulsion units lare mounted is given an initial forward motion of, for example,approximately several hundred miles per hour in the case of the presentdesign. This may be accomplished by means of the ordinary propeller,driven from the engine which drives generator M, or by rocket propulsionunits or the like. ln case a propeller is used, it may be featheredafter the requisite speed is reached. ln the case of the rocketpropulsion unit, its action may cease at the requisite speed. The statedinitial velocity is necessary for providing proper operating conditions.At the requisite speed the circuit 3l is closed at switch d3, whichcauses an are initially to be struck at the 1/4 in. gap

Considering motions relatively to the tube l, the sweep of air from theinlet tube I into the transformation or heater tube T causes this arc tobe blown back along the electrodes 29, the arc lengthening as itrecedes. Traverse of the arc is quite fast, requiring only the timenecessary for air at approximately several hundred miles per hour totraverse the 12 it. section of tube T. At or somewhat ahead oi the pointl the resistance in the arc will have become so high that the arc willbe blown out. Rearward arching due to air sweep aids in the extinctionprocess.

Assuming, as will be approximately true, that the arc operates at ornear 3,509o C., it will, as it travels rearward, exert a fast heatingaction upon the adjacent mass and slug of air in the arc. The airtherefore expands. A high air temperature approaching 3,530 C. isreached at approximately 8 rt. from the gap In the last Ll it. or so oftravel in the tube T the process will be substantially isothermal at thestated temperature. When point l' is reached and the arc becomesextinguished, the air expands further and more rapidly in more taperedexhaust tube E, until a reduced temperature of the order of 700 C. isreached at the outlet section 9.

As the air in the arc is heated, its pressure locally momentarilyincreases to the order of 3 p. s. i. This pressure is of a hydrostaticnature, being exerted momentarily in all directions, both axial andradial. This pressure equilibrates the equivalent dat plate pressure ofthe entering air as applied to the area at the inlet 3. Equilibriurnoccurs ahead of the arc as the arc progresses through tube 'I'. Thedistance that this point is ahead of the are depends upon thetemperature of the slug of air containing the arc. At the temperature ofthe air in the arc, this distance is of the order of several inches. Thestated 3 p. s. i. is approximately the operating flat plate pressure tobe excepted at the inlet 3.

It is to be understood that although this 3 p. s. i. is equilibrated,the equilibrium point progresses rearward through the tube T, lwhichallows admission of cold air immediately following the arc as the latterprogresses rearward. Thus, for example, the amount of hot air containedin the are may be of the order of l5 cu. in., which progresses rearwardvery quickly. Hence the walls of the tube T are subjected to extremetemperatures only for exceedingly short intervals of time.

The momentary pressure oi the mass of gas under consideration also actsupon the sloping surfaces of the tube section T, thus exerting a forwardaxial thrust which drives the tube forward. The expanding gas passes outthrough the exhaust tube E in which its pressure also exerts a forwardthrust by reason o1 the taper of tube E.

The net forward thrust is a function of the difference between the areasof the sections at points 3 and 9, multiplied by 'the equilibratingpressure of the heated gas (3 p. s. i.) during the part of the cyclewhen inflow of additional air occurs, as it follows in to the rearwardlymoving equilibrium point. Some resistance is built up against the freeentry of cold air by the fact that, as heating occurs in the rearwardlymoving arc, the equilibrium point is shifted forward relative to thearc, due to the expansion of the air with increasing temperature. As therearwardly traveling mass of air in the arc expands, it resists theincoming air, applying an opposite impulse to the mass of air behind it.

As the pressure in the tube T decreases after the arc has beenextinguished, the flat plate pressure at the transient equilibrium pointwill become unbalanced and a fresh charge of cool air will have Filledthe tube T. By this time the arc, which in the previous cycle has beenextinguished at point l, will have been automatically reestablished atthe gap 33. Thus the conditions are fully reestablished for a succeedingcycle. Cyclic action is then continuously repetitious, the timing of thearc and of air entry and expansion all being inherent in the process. Nomoving parts are required for the pulse or expansion process or itstiming, no valves of any kind being used.

If the internal pressure in tube T is lower than the equivalent flatplate pressure at inlet 3, the optimum eii'iciency is not attained butthe device is still mechanically operative. In fact, by this meansthrust may be controlled.

The tube under repeated thrust or pulsing will accelerate along its axisuntil the average torward thrust will be equilibrated by irietionalresistance, after which a constant velocity condition will inhere.Velocity is controlled by ccntrolling the electrical energy input ,intothe arc.

Although a very high temperature exists in the mass or slug of air inthe arc, it is not to be assumed that the parts of the tubes T and Eatta-in. any such temperatures. In fact, the tube walls are exposed tohigh temperatures for only very short intervals of time and to the lowtemperatures of the incoming air for much longer intervals of time.Since the weight ratio of the cool incoming air to the hot air in thearc is of the order of 1,00011, this means, assuming that the incomingair is at 0 C., that the walls of the apparatus will never reachtemperatures destructive of even the most commonly available materialsfor the tube, such as, for example, aluminum. This also accounts for theability of the apparatus to reach high efficiencies, because thetemperature to which the arc may be raised is not limited by thestructural materials composing the tube and contained parts.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. A jet propulsion unit comprising an elongate tapering thrust chamberhaving a leading inlet and a larger trailing outlet, movement of tneunit introducing relatively cool gaseous medium through the inlet intosaid chamber, electrodes extending substantially along the length or"the chamber from a first arc-striking point near the inlet to a secondarc extinguishing point near the outlet for drawing an arc at said iirstpoint in the presence of said medium, whereby the medium is heated andejected from said outlet,

said medium due to relative movement between it and the thrust chambermoving the arc from the first point near the inlet to the second pointnear the outlet along the electrodes, the spacing of the electrodes nearthe outlet being sufficient to attenuate the arc to extinction as itreaches said second point near the outlet.

2. A jet propulsion unit comprising an elongate tapering thrust chamberhaving a leading inlet and a larger trailing outlet, a movement of theunit along its length introducing relatively cool gaseous medium throughthe inlet into said chamber, electrodes extending along the length ofthe chamber and being spaced closer together toward the inlet thantoward the outlet for striking an arc at said closer spacing in thepresence of said medium, whereby the medium is heated and ejected fromsaid outlet, said medium due to relative movement between it and thethrust chamber moving the arc from the inlet along the electrodes andtoward the outlet.

3. A jet propulsion unit comprising an elongate tapering thrust chamberhaving a leading inlet and a larger trailing outlet, movement of theunit introducing relatively cool gaseous medium through the inlet intosaid chamber, electrodes extending along the length of the chamber andbeing increasingly spaced toward the outlet for drawing an arc at theircloser spacing in the presence of said medium whereby the medium isheated and ejected from said outlet, said medium due to relativemovement between it and the thrust chamber moving the arc from the inletto the outlet, said electrodes being closer together near the inlet tostrike and maintain the arc as it is moved and being far enough apartnear the outlet to attenuate it to extinction.

4. A jet propulsion unit comprising a tubular arc chamber taperingoutwardly from the front to the rear, said chamber having a forward gasinlet and a rearward gas outlet, elongate electrodes located in said arcchamber which are increasingly spaced from front to rear, circuit meansfor applying current to said electrodes, said electrodes extending froma point of relatively close proximity whereat an arc is automaticallystruck by said circuit means, said electrodes extending to points ofrelatively greater spacing where said arc becomes longer to the point ofextinction, substantially forward velocity of the chamber introducinggas into said inlet to said are to sweep the latter to a point where itwill be extinguished, said arc momentarily heating the introduced gas toexpand it temporarily to resist entrance of further gas into the inletand simultaneously by impingement upon the tapering chamber to apply anaxial forward thrust to said chamber. f

5. Jet propulsion apparatus comprising a moving arc chamber having aleading inlet and a trailing outlet, said chamber being tapered outwardfrom the inlet to the outlet, elongate electrodes extending from arelatively narrow gap toward the inlet to a relatively wider gap towardthe outlet, the movement of the chamber serving to introduce air intothe chamber through said inlet and to move the air rearward through thechamber, means for striking an arc at said relatively narrow gap, saidarc heating and expanding the air whereby its pressure momentarilyincreases, movement of the contained air toward the outlet serving tomove and attenuate the arc until it breaks, pressure of the air on thetapered chamber serving to thrust the tapered arc chamber forward, saidextinguished arc being automatically restruck at the narrow gap asadditional air enters the inlet under the reduced pressure in said arcchamber.

6. A jet propulsion unit comprising an elongate tubular member aringfrom front to rear and having a front gas inlet and a rear gas outlet,

said tubular member having a front inlet section of one taper, anintermediate section of greater taper, and a rear section of stillgreater taper, axially extending electrodes in said intermediatechamber, said electrodes being closely spaced at their forward ends toform a short gap and being increasingly spaced from one another in therearward direction toward a long gap, circuit means supplying current tosaid electrodes, the

'i electrical values associated with said current being such asautomatically to strike an arc at the short arc gap and to permit saidarc to break after traverse backward along the electrodes to the longgap, forward motion of the tubular member effecting introduction of airto blow said arc from said gap to the point of extinction, said gasexpanding against the flaring tubular member to effect a forward thrustthere- GEORGE E. MALLINCKRODT.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 745,805 Ennis Dec. 1, 19031,517,422 Hall Dec. 2, 1924 1,836,994 Slepian Dec. 15, 1931 1,934,518Anderson Nov. 7, 1933 2,377,247 `Lagelbauer May 29, 1945 FOREIGN PATENTSNumber Country Date 20,697 Great Britain Sept. 17, 1907 162,972 GreatBritain May 12, 1921 412,478 France May 3, 1910 288,168 Germany Oct. 21,1915 370,388 Germany Mar. 2, 1923

